Mycoplasma –contamination of cell-culture


Mycoplasmas are the smallest free-living organisms and considered to be the simplest of bacteria. They belong to the bacterial class Mollicutes, whose members are distinguished by their lack of a cell wall and their plasma-like form. The first strains of mycoplasma were isolated at the Pasteur Institute in 1898, and to date, 20 of the roughly 190 known species have been identified as bona fide contaminants of laboratory cell cultures. Owing to their extremely basic genomes, mycoplasmas must function as parasites in order to meet their energy and biosynthesis demands. Thus, they exploit their host’s cells to survive.

Consequences of Mycoplasma contamination in cell cultures

Mycoplasmas compete with host cells for biosynthetic precursors and nutrients and can alter DNA, RNA and protein synthesis, diminish amino acid and ATP levels, introduce chromosomal alterations, and modify host-cell plasma membrane antigens. A microarray analysis on contaminated cultured human cells has revealed the severe effects that mycoplasmas can have on the expression of hundreds of genes, including some that encode receptors, ion channels, growth factors and oncogenes. Moreover, mycoplasmas exert significant effects on cultured immune cells such as monocytes and macrophages.

Detecting, eliminating and preventing mycoplasma contamination

There are three major sources leading to mycoplasma contamination of cell cultures in the laboratory: infected cells sent from another lab; contaminated cell culture medium reagents such as serum and trypsin; and laboratory personnel infected with M. orale or M. fermentans. Furthermore, contamination can spread rapidly to other cell lines through dispersion of aerosol droplets. Once mycoplasmas have been detected, the best solution to eliminate them and to prevent them from spreading is to discard the contaminated cell line. However, valuable cell lines that are too precious to be sacrificed can be salvaged by treatment with effective mycoplasma-eradication products, including mycoplasma-selective antibiotics. These products have been shown to eliminate mycoplasma and to restore cell behavior and responses within days or weeks after treatment.

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Sophie Kate
Managing Editor
Microbiology: Current Research